The present invention pertains to a bottom or wall structure for a metallurgical vessel with a refractory lining, which is adjacent to an outer metallic envelope of the vessel and has, on the side facing away from the metallic envelope, a wear lining, which is permeable to gas in at least some of its sections and covers with its gas-permeable section at least one gas purging device with an associated gas inlet.
Such a bottom structure has been known from DE 37 42 861 C1. A passage opening, within which a metallic tube, which is fixed in the passage opening with mortar, is located in the area of a refractory outer lining. A metallic baffle plate, whose surface area is substantially larger than the cross-sectional area of the passage opening, is arranged in the wear lining immediately above the said passage opening, so that gas admitted via the tube first flows through the said mortar and then a first section of the gas-permeable wear lining before it diffuses further, deflected to the side by the baffle plate, around the outer edges of the baffle plate, through the porous wear material and into the metal melt.
The prior-art bottom lining is provided for an electric arc furnace and it shall ensure, besides long service life, above all introduction of the purging gas distributed over a large area into the metal melt to form a large purging spot in order to ensure a uniform and smooth burning of the arc.
Due to the lateral deflection of the treating gas--in a plane that is essentially parallel to the outer lining or the wear lining--the gas flow is deliberately deflected laterally, as a consequence of which appreciable amounts of gas diffuse laterally in an uncontrolled manner and, above all, undesirably escape to the outside through the outer lining. In addition, the flow rate is markedly reduced due to the distribution of the gas flow, and it is therefore not always possible to penetrate the topmost layer of the wear lining, which will sinter under the effect of the heat, thus becoming gastight. As a result, the purging effect will not be satisfactory.
The melting process in the metallurgical vessel is to be generally facilitated, the rate of decarbonization increased, and the melting energy reduced by a gas purging device.
DE 39 01 926 C1 discloses a gas purging device, in which the purging cone is located within the outer lining, and a finite wear hood made of refractory material is arranged above the gas outlet-side front surface of the purging device instead of a wear lining, wherein the wear hood is approximately in the form of a hemisphere and is designed as a gas-permeable wear hood or is provided with a gas-permeable insert. Diffusion of the gas flow into the wear hood and consequently distribution of the gas fed in take place in this case as well, as a consequence of which the gas flow is reduced, the size of the purging spot is increased, and circulation of the metal melt is possible only under certain conditions.